Rotor cooling means for water-cooled turbogenerators



March 31,1970 'o. TJERNSTROM w 3,504,207

ROTOR COOLING MEANS FOR WATER-COOLED TURBOGENERATORS Filed June 9, 1969 V 2 Sheets-Shea 1 INVENTDR. ova Tnaeusran United States Patent O 3,504,207 ROTOR COOLING MEANS FOR WATER-COOLED TURBOGENERATORS Ove Tjernstrt'im, Irsta, Sweden, assignor to Allmiinna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Filed June 9, 1969, Ser. No. 831,692 Claims priority, application Sweden, June 17, 1968, 8,143/ 68 Int. Cl. H02k 9/16 U.S. Cl. 310-54 4 Claims ABSTRACT OF THE DISCLOSURE A rotor cooling system for a water-cooled turbogenerator has a plurality of cooling channels arranged in the conductor of the rotor winding and a plurality of metal coolant tubes connected to the coil ends of the winding. These coolant tubes have parts extending radially inward into an annular metallic distribution vessel arranged axially outside the coil ends. Individual electrically insulating intermediate sleeves form a connection between the coolant tubes and the distribution vessel.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to a rotor cooling system for water-cooled turbogenerators, which system comprises a plurality of cooling channels arranged in the conductor of the rotor winding and a plurality of metal coolant tubes connected to the coil ends of the rotor winding, the coolant tubes forming by means of their individual electrically insulating intermediate members a hydraulic connection between the coil ends and an annular distribution vessel of metal arranged axially outside the coil ends.

The prior art In a rotor cooling system of this type an extremely high liquid pressure arises in the cooling system due to the centrifugal forces. The high pressure makes considerable demands on the arrangements used to connect the various parts of the system to each other, which means, inter alia, that said distribution vessel must be made of metal, which in turn means that precautions must be taken to prevent electrical connection between the coolant tubes and the walls of the distribution vessel. It is also necessary to ensure that stretches of water between metal parts of different potentials are so long that no current to speak of can be conducted as a creepage current along moist surfaces of intermediate insulating parts. Since the annular distribution vessel expands to to the influence of the centrifugal forces, the mechanical connection between distribution vessel and coolant tubes must be of such a type that corresponding deformations in the coolant tubes are avoided.

A cooling system which, in certain respects, resembles the object of the application is known from German Patent No. 1,014,215. According to that patent glass bodies are melted around the ends of individual cooling tubes at their insertion point into the annular distribution chamber, and thus operate as electrical insulators. The glass melting causes considerable complications in the manufacture and, furthermore, it is questionable whether the risk of cracks occurring in the glass when subjected to temperature variations is impermissibly high.

A similar cooling system is shown in the British Patent No. 977,070 which shows a cooling system having hollow conductors instead of coolant tubes so that the connection with the annular distribution vessel is done with the help of tubes having such thick walls that they can be threaded and joined by means of sockets screwed on. The necessary r 3,504,207 1C Patented Mar. 31, 1970 With a rotor cooling system according to the invention the aim has been to fulfil the requirements of a hydraulic connection between the coil ends and the water-distributing ring, and a construction has been achieved which, in comparison with conventional solutions, allows a considerable reduction in manufacturing and assembly costs. Furthermore, it has the advantage that the connection elements which require inspection and/or repair are very easily accessible. 7

A construction according to the invention presupposes the use of so-called selfsealing jointing rings. By this is meant sealings rings in which the required deformation for scaling is efiected by certain parts of the ring surface being subjected to direct contact with the pressure medium.

Experiments carried out in connection with the development work leading up to the invention have shown that such sealing rings are not always completely reliable as sealing members in machines having a high speed of rotation, for example turbogenerators. It was found'that the reason for this does not lie principally with the high liquid pressure arising at high rotation speed, but with the fact that centrifugal forces deriving from the weight of the ring itself influence the deformation of the ring in an unfavorable manner. With this in mind, a cooling system according to the invention has been arranged with coolant tubes and distribution rings in such a way that the centrifugal forces operating directly on the sealing ring, instead of being a negative factor, contribute considerably to increased sealing. If some substantial part of these centrifugal forces operates perpendicularly to the centre line of the ring, the centrifugal forces operating on the ring in the direction of the component. In a construction according to the invention, this is avoided since the centre line of all the sealing rings is directed radially in relation to the rotor shaft.

A rotor cooling means according to the invention is characterised in that said insulating intermediate member consists of a sleeve directed radially in relation to the rotor shaft, one end of which is inserted in the distribution vessel and the other end of which surrounds the end of the coolant tube at a certain distance from the distribution vessel, each end of the sleeve being provided with a number of annular grooves each containing a selfsealing jointing ring of elastic material, said distribution vessel being arranged at an annular end surface of the rotor core and said sleeve being retained between said end surface and a fixing means arranged outside this end surface.

BRIEF DESCRIPTION OF THE DRAWINGS In the following the invention will be described with reference to the accompanying schematically drawings where FIGURE 1, partly in axial section, partly in partial radial view, shows a turborotor provided with a cooling system according to the invention, while FIG- URE 2 shows in axial section a detail of the means shown in FIGURE 1. FIGURE 3 shows a partial cross section along the line AA in FIGURE 1.

3 DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings 1 designates the rotor core and 2 the center line of a rotor of radial slot type intended for a turbogenerator. The line 3 indicates the bottom of a winding slot. The coil ends of the rotor Winding are designated 4, the retaining ring 5 and the end ring 6.

The rotor winding is directly cooled by means of thinwalled cooling tubes 7a embedded in the conductors and interconnected to communicate with each other in conventional manner. The system of communicating cooling tubes is, at the'rotor end shown in the figure, directly connected to a plurality of coolant inlet tubes 7 and at the other end to similar'coolant outlet tubes. The coolant inlet tubes 7 are led from the coil ends 4 through axial channels in an annular-support member 8 of insulating material surrounding the rotor body. Radially inside the casing support ring 6 the coolant tubes are bent at right angles and directed radially inwards along the end surface of the rotor core'being electrically insulated from the rotor iron and each other and held by means of an annular support means arranged at the flank surface of the rootr body and having radial slots, said support means containing a metallic pressure .ring 9 which is pressed axially inwards with the help of bolts which are indicated in the drawings by the center lines 21 and 22. The ends of the coolant inlet tubes are connected to a distribution chamber 10 formed by an annular, metallic distribution vessel 11, the radially outer wall of which is provided with radially directed recesses for hydraulic connections with the coil ends 4. The distribution vessel 11 is attached to an annular end surface 30 of the rotor core by means of stop surfaces 12 and 13 and also with the help of the pressure ring 9 which with its outer edge abuts the end ring 6. The radially inner wall of the distribution ring is provided with recesses for a number of feeding tubes 24 which are in communication with a centrally arranged axial inlet channel for cooling liquid 26. For manufacturing reasons the rotor body is designed with a removable part 23. The end of the rotor not shown in the drawings is constructed in the same way as the end shown in FIGURE 1, with the difference that the part corresponding to the annular distribution vessel 11 is connected to the outlet channel 29 instead of the inlet channel 216.

A water-tight connection between the coolant tubes 7 and the distribution ring 11 is effected with the help of self-sealing elastic jointing rings 14 and 15. With the intention of enabling the exchange of sealing rings without having to dismantle the distribution ring 11 or the ends of the coolant tubes, and with a view to obtaining reliable electrical insulation between coolant tubes 7 and distribution ring 11, the ends of the coolant tubes are not inserted completely into the distribution ring, but instead the cooling liquid is led through an electrically insulating sleeve 16 across a gap between the end 28 of the coolant tube and the distribution ring. In order to achieve increased insurance against creepage currents, the sleeve 1'6 is provided with a tightly surrounding hose 17 of very elastic insulating material, which also surrounds an adjacent part of the cooling water tube 7. The sleeve 16 is inserted in a radial recess in the distribution vessel recess in the distribution vessel and sealed to the walls of the recess by means of the elastic sealing rings 15 which permit the sleeve 16 to move in radial direction in relation to the rotor shaft. The radial freedom of movement is limited, however, since the sleeve 16 and the insulating hose 17 are surrounded by a support sleeve 18 which is porting sleeve which comprises two halves arranged toin two parts, divided by a cut 31 in its longitudinal direction and shaped a stop surface 19 to take up centrifugal forces operating on the sleeve 16. The support sleeve 18 is arranged in a radial channel 27 which is symmetrical in relation to the contact surface 20 between the pressure ring 9 and the rotor part 23. The support sleeve is securied against centrifugal forces since its end abuts contact surfaces in the channel 27. The end of the cooling water tube 7 is inserted into the radially outer end of the sleeve 16 and surrounded by the self-sealing elastic jointing rings 14.

If the jointing rings 14 and 15 must be changed, the pressure ring '9, the two halves of the support sleeve 18 and the locking ring 25 are removed. The elastic insulating hose 17 is peeledupwardly to the space radially outside the sleeve 16, which is then displaced radially inward or outward so that the sealing rings 14 or 15, respectively, become "accessible.

What is claimed is:

1. Rotor cooling system for water-cooled turbogenerators, which comprises a plurality of cooling channels arranged in the conductor of the rotor winding and a plurality of metal coolant tubes connected to the coil ends of the rotor winding and including parts extending radially inward, an annular metallic distribution vessel arranged axially outside, the coil ends, individual electrically insulating intermediate members forming a hydraulic connection between the coil ends and the annular distribution vessel, said insulating intermediate members each comprising a sleeve directed radially in relation to the rotor shaft, one end of which is inserted in the distribution yessel and the other end of which surrounds the end of a radial coolant tube part at a distance from the distribution vessel, each end of the sleeve being provided with at least one annular groove, said grooves each containing a self-sealing jointing ring of elastic material, said distribution vessel being arranged at an end'surface of the rotor core and a fixing means arranged outside said end surface, said sleeve being retained between said end surface and said fixing means.

2. Cooling system according to claim 1, in which said fixing means comprises a fixing ring and means to press the fixing ring against the end surface of the rotor core, and in which members forming channels for radial tube parts are arranged substantially so that they are halved by planes through adjacent contact surfaces between the support ring and the rotor core, each channel having a radially outer part which tightly surrounds a radially directed tube part surrounded by insulating material and a wider, radially inner part which also surrounds said sleeve.

3. Cooling system according to claim 2, in which a flexible, insulating hose surrounds said sleeve and a part of the tube which lies immediately radially outside the sleeve.

4. Cooling system according to claim 3, in which a supgether. and divided symmetrically to a plane perpendicular to the rotor shaft surrounds said insulating base.

References Cited UNITED STATES PATENTS 2,950,403 8/1960 Kilne et al. 310-61 X 3,034,003 5/1962 Seidmer 310-61 3,131,321 4/1964 Gibbs et al. 1054 3,296,470 1/ 1967 Barbashev et al. 3l054 3,340,412 9/1967 Wiedemann 310-61 X DONOVAN F. DUGGAN, Primary Examiner US. Cl. X.R. 310-59, 61 

